Abstract
We report herein the first visible light optical coherence tomography angiography (vis-OCTA) for human retinal imaging. Compared to the existing vis-OCT systems, we devised a spectrometer with a narrower bandwidth to increase the spectral power density for OCTA imaging, while retaining the major spectral contrast in the blood. We achieved a 100 kHz A-line rate, the fastest acquisition speed reported so far for human retinal vis-OCT. We rigorously optimized the imaging protocol such that a single acquisition took < 6 seconds with a field of view (FOV) of 3×7.8 mm2. The angiography enables accurate localization of microvasculature down to the capillary level and thus enables oximetry at vessels < 100 µm in diameter. We demonstrated microvascular hemoglobin oxygen saturation (sO2) at the feeding and draining vessels at the perifoveal region. The longitudinal repeatability was assessed by < 5% coefficient of variation (CV). The unique capabilities of our vis-OCTA system may allow studies on the role of microvascular oxygen in various retinal pathologies.
Highlights
Visible light optical coherence tomography [1,2,3,4,5,6,7,8,9,10,11] is a new derivation of OCT that uses visible light laser illumination instead of a conventional near-infrared (NIR) light [12]
We collected a dataset by numbers of repetitive frames (Nrep) = 12, and processed vis-OCTA images from the first Nrep frames for Nrep = 2, 4, 6, 8, 12
In this paper, we describe the first vis-OCTA imaging of human retina using a redesigned spectrometer and optimized imaging protocol allowing for enhanced vascular signal and localization of the microvasculature
Summary
Visible light optical coherence tomography (vis-OCT) [1,2,3,4,5,6,7,8,9,10,11] is a new derivation of OCT that uses visible light laser illumination instead of a conventional near-infrared (NIR) light [12]. One advantage of vis-OCT is its spatio-spectral analysis within the microvasculature for label-free oximetry (i.e. measuring hemoglobin oxygen saturation, sO2) [4,13,14,15,16,17,18,19]. The first demonstration of vis-OCT dates back to 2002 [22], but the first in vivo vis-OCT retinal imaging was not reported until 2013 [4]. The first demonstration of vis-OCT retinal oximetry was reported in 2013 in a rat retina, showing the sO2 calculations in the major arterioles and venules immediately exiting and entering the optic nerve head (ONH) [4]. Human retinal imaging by vis-OCT was demonstrated in 2015 [27] and human retinal oximetry by vis-OCT was reported in 2017 [13,17]
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